Beverages that are designed to rehydrate the body are well known. These products provide electrolytes and carbohydrates in proportions and levels that are easily adsorbed by the body. They can be designed for use during strenuous physical exertion, relief of dehydration caused by nausea and/or diarrhea, or for efficient delivery of vitamins, minerals and/or drugs. Some ready-to-drink (RTD) products that deliver these benefits include Gatorade®, Powerade®, and Pedialyte®.
One of the keys to delivering these benefits is to assure that the beverage has the proper osmolality. Osmolality is a measure of the number of dissolved particles in a solution. Normal body fluids have a natural osmolality of about 280-302 mOsm/kg. Beverages that have lower osmolality than this are considered hypotonic; those with osmolality in this range are isotonic; those with greater osmolality are hypertonic. In general, hypotonic and isotonic products provide the best rehydration benefits. Slightly hypertonic products may also be acceptable.
Beyond the osmolality of the product, the amount of electrolyte and carbohydrate that it provides are also important for delivery of the intended benefit. The World Health Organization (WHO) recommends that Oral Rehydration Salts for treatment of diarrhea deliver the following range of glucose and electrolytes:                Glucose: Not more than 111 mmol/l        Sodium: 60-90 mEq/l        Potassium: 15-25 mEq/l        Citrate: 8-12 mmol/l        Chloride: 50-80 mEq/lTotal substance concentration (including glucose): 200-310 mmol/l        
A formulation favored by WHO is:                Sodium Chloride: 2.6 g/l        Glucose, Anhydrous: 13.5 g/l        Potassium Chloride: 1.5 g/l        Trisodium Citrate, Dihydrate: 2.9 g/lThis formula delivers:        Sodium: 75 mmol/l        Chloride: 65 mmol/l        Glucose, Anhydrous: 75 mmol/l        Potassium: 20 mmol/l        Citrate: 10 mmol/l        Total Osmolality: 245 mOsm/kg        
The WHO recommended product is intended to be delivered as a powder that is dissolved in water just prior to use. WHO acknowledges that this composition can be delivered in liquid or tablet form, but notes that these forms may not be as economical to produce or distribute as powders.
Effervescent rehydration tablets that are designed to dissolve in water to form beverages have been marketed. Servidrat® and Servidrat LS® from Novartis are available in Latin America and other parts of the world. They are used primarily in areas where disease is endemic or where natural disasters have occurred. They are unflavored products that result in salty solutions. They would not be acceptable for commercial sale as consumer products.
It is noteworthy that the WHO acknowledges that color and flavor can be added to Oral Rehydration Salts in order to increase consumer acceptability. However, they reference studies conducted in Egypt and the Philippines that indicate no advantages or disadvantages with regards to safety, acceptability and correct use for flavored/colored product.
Electrolytes are essential to formulating an effective rehydration drink. As shown in the WHO formula above, these materials are generally incorporated as chloride salts. Naturally, these chloride compounds taste salty. This can present a challenge to those attempting to formulate an acceptable tasting product.
From a chemist's point of view, electrolytes are materials that ionize in solution, thus allowing electricity to be conducted. Many organic and inorganic materials meet this requirement. From a physiologist's view point, the important electrolytes are limited to sodium, potassium, chlorine, magnesium, calcium and bicarbonate. For purposes of this invention, electrolytes will be defined as the ionic forms of sodium, potassium, magnesium, calcium, bicarbonate and chlorine. Ions of edible acids such as citrate, tartrate, malate and fumarate are also included as electrolytes.
Carbohydrates are usually included in rehydration drinks. Glucose is known to accelerate the adsorption of both water and dissolved materials in the small intestine. Carbohydrates also contribute to the osmolality of the product and they provide calories that the consumer generally needs. They also tend to add sweetness to the product. This improves consumer acceptability. Glucose, dextrose, and sucrose are the most commonly used carbohydrates. Other carbohydrates include galactose, fructose, lactose and maltose. Maltodextrin and other glucose polymers are also used when the formulator intends that carbohydrate provide a more sustained release of energy (be metabolized more slowly) than it would be with monomer or dimer sugars.
Effervescent tablets that create beverages upon dilution are known. Tablets that deliver vitamins are popular in Europe. Many of these products deliver some level of electrolyte either by design or by the fact that sodium and/or potassium is delivered by the sodium and/or potassium bicarbonate used in the effervescent couple. These products generally do not contain carbohydrates. When carbohydrates are included, they are generally present only at minimal levels. It is hypothesized that these levels are used to improve product performance parameters (such as dissolution rate or sweetness profile) or processability. There would be minimal impact on osmolality.
As noted above, RTD consumer products such as Gatorade®, Powerade®, and Pedialyte® are designed for rehydration benefits. As shown in the table below, these products offer a range of carbohydrate and electrolyte levels (expressed in mmol/liter). Electrolyte and carbohydrate levels for the WHO and Servidrat® products are shown for comparison purposes.
ServidratGatorade ®Powerade ®Pedialyte ®WHOServidrat ®LS ®Sodium201045759056Potassium3320202020Chloride201035658046Bicarbonate00003030Citrate000103030Total Electrolyte4323100170250182Dextrose33035013975100140Other050000CarbohydrateTotal33035514075100140CarbohydrateOsmolality280-360403255245306290(mOm/kg)
It is noteworthy that the RTD sports drinks (Gatorade® and Powerade®) are formulated to give higher carbohydrate levels than the WHO and Servidrat® products. This is not surprising as the sports drinks are designed to boast the user's energy levels by providing readily available calories from simple sugars. It is also interesting to note that all of the commercial products have less electrolyte than the WHO and Servidrat® products. This was probably done to minimize salty taste, making the product more palatable to consumers.
U.S. Pat. No. 3,337,404 teaches effervescent potassium compositions. The compositions comprise potassium bicarbonate, potassium chloride, citric acid, sweeteners and fillers. There is no discussion of how much the water the composition should be dissolved in, so it is not possible to calculate the molar concentration of the various ions. Needless to say, there is no discussion of the osmolality or flavor of the resultant solution.
U.S. Pat. No. 5,114,723 teaches a hypotonic aqueous beverage composition with particular electrolyte and carbohydrate levels. This patent does not lead one skilled in the art to contemplate delivery of these materials in a solid tablet or granule form.
U.S. Pat. No. 5,164,192 relates to specific effervescent compositions for oral rehydration of domestic or companion animals that are suffering from diarrhea. This patent requires the use of lactose and/or amino acids. Thus, this composition would not be useful to persons that are lactose intolerant.
It is the aim of this invention to provide effervescent tablet and granule compositions that deliver electrolytes and carbohydrates at levels that result in hypotonic, isotonic or slightly hypertonic solutions when dissolved in appropriate amounts of water. These formulations are created with electrolyte and carbohydrate levels that are high enough for rehydration but low enough for acceptable taste.
Edible acids and carbonate salts are included in the inventive compositions in order to make them effervescent. Effervescence helps the product dissolve completely and it distributes the components of the product uniformly in the beverage solution. Flavors, sweeteners, and/or colors are included in preferred embodiments. Vitamins, drugs, herbal materials, minerals and other dietary supplements can be added if the formulator desires.